/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *  http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mlizhi.base.codec.language;

import com.mlizhi.base.codec.EncoderException;
import com.mlizhi.base.codec.StringEncoder;


/**
 * Encodes a string into a Refined Soundex value. A refined soundex code is
 * optimized for spell checking words. Soundex method originally developed by
 * <CITE>Margaret Odell</CITE> and <CITE>Robert Russell</CITE>.
 * 
 * @author Apache Software Foundation
 * @version $Id: RefinedSoundex.java 797690 2009-07-24 23:28:35Z ggregory $
 */
public class RefinedSoundex implements StringEncoder {

/**
 * @since 1.4
 */
public static final String US_ENGLISH_MAPPING_STRING = "01360240043788015936020505";

   /**
 * RefinedSoundex is *refined* for a number of reasons one being that the
 * mappings have been altered. This implementation contains default
 * mappings for US English.
 */
public static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();

/**
 * Every letter of the alphabet is "mapped" to a numerical value. This char
 * array holds the values to which each letter is mapped. This
 * implementation contains a default map for US_ENGLISH
 */
private final char[] soundexMapping;

/**
 * This static variable contains an instance of the RefinedSoundex using
 * the US_ENGLISH mapping.
 */
public static final RefinedSoundex US_ENGLISH = new RefinedSoundex();

 /**
 * Creates an instance of the RefinedSoundex object using the default US
 * English mapping.
 */
public RefinedSoundex() {
this.soundexMapping = US_ENGLISH_MAPPING;
}

/**
 * Creates a refined soundex instance using a custom mapping. This
 * constructor can be used to customize the mapping, and/or possibly
 * provide an internationalized mapping for a non-Western character set.
 * 
 * @param mapping
 *  Mapping array to use when finding the corresponding code for
 *  a given character
 */
public RefinedSoundex(char[] mapping) {
this.soundexMapping = new char[mapping.length];
System.arraycopy(mapping, 0, this.soundexMapping, 0, mapping.length);
}

/**
 * Creates a refined Soundex instance using a custom mapping. This constructor can be used to customize the mapping,
 * and/or possibly provide an internationalized mapping for a non-Western character set.
 * 
 * @param mapping
 *Mapping string to use when finding the corresponding code for a given character
 * @since 1.4
 */
public RefinedSoundex(String mapping) {
this.soundexMapping = mapping.toCharArray();
}

/**
 * Returns the number of characters in the two encoded Strings that are the
 * same. This return value ranges from 0 to the length of the shortest
 * encoded String: 0 indicates little or no similarity, and 4 out of 4 (for
 * example) indicates strong similarity or identical values. For refined
 * Soundex, the return value can be greater than 4.
 * 
 * @param s1
 *  A String that will be encoded and compared.
 * @param s2
 *  A String that will be encoded and compared.
 * @return The number of characters in the two encoded Strings that are the
 * same from 0 to to the length of the shortest encoded String.
 * 
 * @see SoundexUtils#difference(StringEncoder,String,String)
 * @see <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp">
 *  MS T-SQL DIFFERENCE</a>
 * 
 * @throws EncoderException
 *  if an error occurs encoding one of the strings
 * @since 1.3
 */
public int difference(String s1, String s2) throws EncoderException {
return SoundexUtils.difference(this, s1, s2);
}

/**
 * Encodes an Object using the refined soundex algorithm. This method is
 * provided in order to satisfy the requirements of the Encoder interface,
 * and will throw an EncoderException if the supplied object is not of type
 * java.lang.String.
 * 
 * @param pObject
 *  Object to encode
 * @return An object (or type java.lang.String) containing the refined
 * soundex code which corresponds to the String supplied.
 * @throws EncoderException
 *  if the parameter supplied is not of type java.lang.String
 */
public Object encode(Object pObject) throws EncoderException {
if (!(pObject instanceof String)) {
throw new EncoderException("Parameter supplied to RefinedSoundex encode is not of type java.lang.String");
}
return soundex((String) pObject);
}

/**
 * Encodes a String using the refined soundex algorithm.
 * 
 * @param pString
 *  A String object to encode
 * @return A Soundex code corresponding to the String supplied
 */
public String encode(String pString) {
return soundex(pString);
}

/**
 * Returns the mapping code for a given character. The mapping codes are
 * maintained in an internal char array named soundexMapping, and the
 * default values of these mappings are US English.
 * 
 * @param c
 *  char to get mapping for
 * @return A character (really a numeral) to return for the given char
 */
char getMappingCode(char c) {
if (!Character.isLetter(c)) {
return 0;
}
return this.soundexMapping[Character.toUpperCase(c) - 'A'];
}

/**
 * Retreives the Refined Soundex code for a given String object.
 * 
 * @param str
 *  String to encode using the Refined Soundex algorithm
 * @return A soundex code for the String supplied
 */
public String soundex(String str) {
if (str == null) {
return null;
}
str = SoundexUtils.clean(str);
if (str.length() == 0) {
return str;
}

StringBuffer sBuf = new StringBuffer();
sBuf.append(str.charAt(0));

char last, current;
last = '*';

for (int i = 0; i < str.length(); i++) {

current = getMappingCode(str.charAt(i));
if (current == last) {
continue;
} else if (current != 0) {
sBuf.append(current);
}

last = current;

}

return sBuf.toString();
}
}
